Electrical Stimulation
The use of various forms of electrical current in augmenting tissue repair was reported as early as the 1600s when charged gold leaf was used to prevent scarring in smallpox survivors (Kloth & Feedar 1988). The therapeutic effects of electrical stimulation for wound healing have been well documented since the 1960s, especially for wounds not responding to standard forms of treatment (Kloth & Feeder 1988; Bogie et al. 2000).
Galvanotaxis is the process by which electrical stimulation directs cell movement and it is thought to be a process that can impact wound healing through the migration of cells such as epithelium, macrophages, neutrophils and fibroblasts (Feedar et al. 1991; Bogie et al. 2000). Under normal circumstances there is a flow of charged particles from an uninjured area to an injured area triggering a biological repair system. The belief is that application of exogenous electrical current should be able to enhance healing in non-healing wounds by mimicking the body’s own healing system (Carley & Wainapel 1985). A second theory purports that the application of electric current activates cutaneous nerves and creates a centrally mediated increase in circulation to the wound to indirectly promote healing (Kaada 1982). Despite the increasing use of electrical stimulation to promote wound healing, there remains a lack of clear understanding as to how it works to repair tissue (Bogie et al. 2000).
Some of the documented effects of electrical stimulation on wound healing include decreased healing time, increased collagen synthesis, increased wound tensile strength, increased rate of wound epithelialization and increased bactericidal and bacteriostatic effects (as cited in Kloth & Feedar 1988). Electrical stimulation has also been shown to indirectly improve healing by improving tissue perfusion and reducing edema formation (Houghton & Campbell 2007). The studies on electrical stimulation for wound healing have examined low-intensity direct current, high voltage pulsed direct current, and alternating current. The literature shows a high variability as to which protocols are the most effective for a specific patient or ulcer (Bogie et al. 2000).
The use of electrical stimulation to promote closure of pressure injuries, when combined with standard wound interventions, has been recommended in both the able bodied and individuals with SCI. Most studies discuss the adjunctive role of electrical stimulation in pressure injuries which have failed to respond to standard treatments (Houghton et al. 2013; Consortium of Spinal Cord Medicine 2000; Keast et al. 2006; AHCPR, Executive Summary # 15 1992).
Discussion
Karsli et al (2017) compared the efficacy of high-voltage electrical stimulation (HVES) with ultrasound (US) in treating Stage II through Stage IV pressure injuries of hospitalized patients. Pressure injuries of patients in the HVES and US groups healed at a mean rate of 43% and 63%, respectively. There was no statistically significant intergroup difference in healing found after treatment. Therefore, study authors concluded that both HVES and US are promising methods for wound healing, and both electrotherapy modalities have been demonstrated to support the healing of pressure injuries.
Recio et al. (2012) conducted a retrospective case series examining the effects of high voltage electrical stimulation (HVES) one hour per day, 3-5 times per week on healing recalcitrant pressure injuries in subjects with SCI. HVES was shown to enhance healing of Stage III and IV pressure injuries that were unresponsive to standard wound care. Recalcitrant pressure injuries (11-14 months) were completely closed within 7-22 weeks of treatment with HVES.
Houghton et al. (2010) conducted a randomized single blind study evaluating the effects of high voltage pulsed current (HVPC) with standard wound care for healing pressure injuries in community dwelling patients with SCI. Subjects who received HVPC showed a significant decrease in percent wound surface area (WSA) after three months compared with those who received standard wound care alone (p=0.048). The proportion of Stage III, IV, and unstageable ulcers in which WSA improved ≥50% was significantly higher in the HVPC group than the standard wound care group (p=0.02).
Adegoke and Badmos (2001) randomly treated six stage IV pelvic pressure injuries with standard nursing care augmented with interrupted direct current or with placebo IDC. Subjects treated with IDC and nursing care showed a decrease in WSA by 22.2% versus 2.6% in the placebo group.
Cukjati et al. (2001) randomly divided participants into four treatment groups: biphasic current, direct current, sham treatment, and conservative treatment. Wounds treated for two hours with biphasic current healed significantly faster than sham-treated wounds (p=0.018) and conservative therapy, but healed at similar rates as direct current (p=0.170). Although wounds treated with direct current healed faster than sham treated wounds, the difference was not statistically significant. (p=0.085).
Karba et al. (1997) demonstrated that when using direct current, placement of the positive stimulation electrode covering the pressure injury and the negative electrodes on intact skin resulted in a greater relative healing rate per day (7.4%, p=0.028) compared to when the positive and negative electrodes were both placed on intact skin on opposite sides across the wound (4.8%)
Baker et al. (1996) showed that for ulcers that responded to any form of electrical simulation (“good responses”), asymmetric biphasic stimulation (group A) was most effective for enhanced wound healing. Wounds that were already showing healing in the control group, with the addition of either protocol A or B (symmetrical Biphasic) showed that healing rate was greater (43.3% Δ/week) when compared to control period (9.7% Δ/week).
Jerčinović et al.(1994) demonstrated that pressure injuries in patients with SCI treated with low frequency pulsed current and conventional therapy for four weeks had a significantly (p=0.006) higher healing rate than those treated with conventional therapy alone. Subjects in the conventional group who crossed over to the electrical stimulation group after fours had improved healing rates in 19 out of the 20 subjects.
Stefanovska et al. (1993) treated 150 pressure injuries in individuals with SCI with conventional therapy alone, or in combination with direct or alternating current. Wounds treated with low frequency pulsed current (alternating current) showed significantly better healing rates than those treated with direct current or conventional treatment alone after the exclusion of deep, superficial and long-term wounds.
Griffin et al. (1991) also performed a randomized controlled trial showing the efficacy of HVPC for healing pelvic pressure injuries in subjects with SCI. When compared to the placebo group, subjects treated with HVPC showed a greater percentage decrease in WSA at day 5 (p=0.03), day 15 (p=0.05) and day 20 (p=0.05).
While there were differences in the type and duration of electric current applied in the nine studies, and in some cases electrode placement, all of the studies demonstrated that when used in conjunction with standard wound management electrical stimulation accelerates the healing rate of pressure injuries in patients with SCI. More study is needed to determine optimum electric current and application protocols to enhance healing of pressure injuries post SCI. Mittman et al. (2011) reported that in additional to standard wound care, electrical stimulation results in a cost savings of $224 over a one-year time frame for treating stage III and IV pressure injuries in individuals with SCI. The cost-savings associated with improved healing rates offset the cost of adding electrical stimulation to standard practice.
Conclusion
There is level 1 evidence (from seven RCTs: Karsli et al. 2017; Houghton et al. 2010; Cukjati et al. 2001; Adegoke & Badmos 2001; Karba 1997; Jercinovic 1994; Griffin 1991) that electrical stimulation accelerates the healing rate of stage III and IV pressure injuries when combined with standard wound management.
